The major goal of Project 4 'is to test the hypothesis that a specific pancreatic cell type or lineage is sensitive to the transforming potential of activated Kras and serves as the cell-of-origin for PDAC in mouse models and in humans. This will be approached in Specific Aim 1 by examining PanlNs and other early lesions from mouse models generated in Project 1 using a series of lineage and developmental markers as well as gene expression profiling. Working with Project 2, biochemical analysis of signaling pathways will be investigated in these early lesions as well. Human tumor material (provided by the BioBank and the Experimental Pathology Cores) will be examined based on information derived from the mouse studies. Necessary immunological reagents not available commercially will be supplied by the PDAC Antibody Core. Unique cell surface markers of early lesions may be used by the Molecular Imaging Core for the purpose of early detection. In Specific Aim 2, we will use existing mouse strains and develop others to create an adult-onset model of PanIN and PDAC. This will involve both the use of viral vectors for delivery Cre recombinase to adult pancreas and knock-in mouse strains in which Cre activity is controlled both specially and temporally. The latter approach will establish what cells and lineages in the adult pancreas are sensitive to oncogenic transformation by Kras. Differential biological responses of various cell types will be correlated with biochemical and signaling differences determined with Project 2. Project 4 will also investigate whether PDAC harbors distinct subsets of cells that function as "cancer stem cells." This will be achieved in Specific Aim 3 though flow cytometric analysis of tumor-derived cells for stem/progenitor cell markers. Both mouse and human material will be examined (provided by Project 1 and the BioBank Core). Sorted cell populations will be tested for relative tumorigenic properties, and isolated cells will be used for additional molecular profiling studies. The characterization of a "cancer stem cell" component of PDAC has important implication for therapy, and the tools developed by Project 4 will be used by Project 3 to examine this population as a function of therapeutic intervention. This effort will be aided by PDAC Antibody Core (which will provide antibodies against unique PDAC cancer stem cell markers) and the Molecular Imaging Core (which will develop methods for their identification in vivo). Project 1 will examine the cancer stem cell population for recurrent genomic alterations. We expect that the identification and functional characterization of these cell types/cell states will provide essential information for improved therapy, diagnosis and early detection of PDAC.